The RS232 LED never light on the BWK-301R

1.Problem description:BWK301R wireless handle. The Power light is on. Press the remote control button and the RF-LED also lights up. But the RS232-LED never lights up. 6445G is used.
2.Analysis:If the handle corresponds to a usable board, change the board to use, replace the terminal used for board connection, and eliminate the board and terminal problems, it may be a problem with the handle.